G protein coupled receptors (GPCRs) are a family of membrane proteins that mediate the biological actions of neurotransmitters and hormones and are a major target for pharmaceutical drug development. Of the top 200 best selling drugs, over 40 of them target GPCRs and those drugs generate over $20 billion. At least 5 percent of the Human Genome expresses receptors, the vast majority of which are orphan receptors for which functions and selective ligands have not been identified. These orphan receptors could provide an important new family of targets for drug development. However, there are few, if any, assays that can be successfully employed to identify drugs against these receptors. In our Phase I SBIR grant, we developed a cell-based assay that can detect GPCR activation using our proprietary CEDIA technology. Specifically, we developed an assay to measure receptor activation of NFkB/IkB signaling. The promiscuity of intracellular signaling pathways linked to NFkB/IkB signaling provides an ideal basis for an assay to measure orphan receptors. The objective of this Phase II SBIR grant is to develop this receptor assay to the point of commercialization. We will determine the breath of applicability of our GPCR assay to measure stimulation of receptors acting via different second messenger signaling pathways as well as measuring responses to orphan receptor activation. We will optimize our assay to be measured in HTS format. To expand the utility of our GPCR assay, we will adapt the assay to directly measure the translocation of NFkB to the nucleus as a response to GPCR stimulation so that the entire assay can be done in intact cells in a very simple and easy-to-use format. In addition to measuring responses to GPCR activation, our NFkB/IkB signaling assay measured the stimulation of growth factor receptor activation. In this grant we will develop and optimize our assay to measure responses to growth factors to commercialize the first HTS assay for growth factor receptor antagonists. The goal of DiscoveRx is to develop a suite of technologies that can aid in the discovery of a new generation of therapeutically important drugs that act upon the large family of orphan GPCRs and growth factor receptors. PROPOSED COMMERCIAL APPLICATION: We will develop a HTS assay to discover drugs against the large family of orphan GPCRs. This market is in the billions of dollars. We will also be able to commercialize an assay for the large family of growth factor receptors which is a comparable size market. Finally, our nuclear translocation assay will be commercialized as a GPCR screen, but will also have applications in the discovery of drugs against transcription factors and drugs to modify gene expression.